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Investigation of the microstructure showed the primary alpha grains to align with the direction of torsion for the forward test and return to an equiaxed shape on strain reversal, though a significant numbers of deformation twins are formed and retained after the full strain reversal.
Misorientation analysis of the αP grains shows misorientation accumulations of up to 20˚ in individual grains, indicating that a significant amount of the applied macroscopic strain was accommodated by the αP grains.
This change in strain path has also returned elongated αP grains back to an equiaxed structure.
This observation may explain the significant drop in σss on strain reversal as grains of favourable orientation have reduced their dislocation density, reducing the effective number of barriers to further dislocation movement.
Upon reversal there is significant reduction in the accumulated misorientation within the αP grains

In addition, Ta element has effect on grain refinement and the number of γ′-Co3(Al,W) phase refines grain.
Cobalt, Tungsten, Aluminum, Tantalum powders purity and grain size are 99.95%, 99.96%, 99.5%, 99.9%, -300, -200, -325 and -200 meshes, respectively.
The 9.8W alloy grain is strips, but the grains of 2Ta alloy is ball rod along, and a large number of white particles at grain boundary precipitation on the matrix, the precipitation is γ'-Co3(Al,W) phase or A3B-type phase, which cannot be determined.
(2) Addition of alloying elements Ta can increase the number of γ' phase and refine grains of Co-8.8Al-9.8W superalloy, the high temperature properties of Co-Al-W superalloy is improved

Recrystallization kinetics and grain size distributions instead of average grain size values were computed for different rolling schedules.
Introduction In recent years, a number of microstructure models[1-12] have been establish to gain a detailed knowledge of metallurgical phenomena in thermomechanical control process (TMCP), i.e.
The predicted final austenite grain size is about 23µm.
It is seen from this figure that the ferrite grain sizes at the surface are close to the ones at the centers and there are the smallest grain sizes at the side.
Here, the retained strain and austenite grain size are the major factors affecting the ferrite grain size after transformation.

Measured structural characteristics were the profile intensities NA (the mean number of grain profiles per unit area of the section plane) and the chord intensities NL (the mean number of profile chords per unit length of the test line).
The estimate of the grain intensity NV (the mean number of grains per unit volume) was obtained following the recommendation of the ASTM E-112 Standard [11] as [NV] = 0.8Π(NA) 3/2, where Π denotes the geometric mean of NA(•), (for a discussion of this relation see [12, 13]).
The surface intensity SV (the mean grain boundary area per unit volume) was estimated as [SV] = 2ENL and the length intensity of grain boundary junctions LV (the mean length of triple grain junction per unit volume) as [LV] = 4ENA, where E denotes the arithmetic mean with respect to all examined planes or directions (the relation [SV] = 2ENL is the standard stereological relation, the relation [LV] = 4ENA follows from the fact that the mean number of profile vertices is 6, hence 2ENA estimates the mean number PA of triple points per unit section area and [LV] = 2PA is again the standard stereological relation).
The estimated mean grain volumes are of the same order - 4 and 12 µm3, but a grain of the volume exceeding 10 4 µm3 (see [10]).
Lowe (editors): Ultrafine Grained Materials III.

In this strain range, grain size (thickness) results from both the convection and the migration of grain boundaries.
Grain size, or rather grain thickness, is determined by the combination of convection and migration of the grain boundaries [4].
However, a number of metallographic investigations carried out on b titanium alloys and an aluminium alloy have shown that the measured average thickness Hexp is systematically larger than H [4].
In fact the true origin of average grain growth is the disappearance of grains when boundaries impinge together.
At intermediate strains, grains become strongly serrated in association with the generation of a large number of subgrain boundaries.

At the beginning of the deformation, a large number of dislocations generated, glided and scrambled in the alloy, then entwisted to form dislocation cells, which were the recrystallization nucleus.
The average grain size is 20~30μm.
As the increasing of deformation, a large number of dislocations propagate, glide and scramble, so the deformation can keep going.
During the dynamic recrystallization, owing to the driving force, the grain boundary move and the recrystallization grain grows, when the grain boundary meet the primary γ’ phase, due to the pinning effect of the primary γ’ phase, the grain growth stop.
At the beginning of the deformation, a large number of dislocations generate, glide and climb in the alloy, then entwist to form dislocation cells, which are the recrystallization nucleus.

The types and number of grain boundaries after heat treatment at 1290°C, 1310°C and 1330°C were counted and the results are shown in Fig. 3.
The number of low-angle and medium-angle grain boundaries was significantly reduced and the proportion of high-angle grain boundaries increased after heat treatment at 1290°C.
Since low-angle grain boundaries and medium-angle grain boundaries are generally the boundaries between sub grains or other crystalline substructures, the more of both, the greater the number of sub grains or substructures.
This reduces the number of low-angle and medium-angle grain boundaries.
When the heat treatment temperature was increased to 1330°C, the sum of the number of low-angle grain boundaries and medium-angle grain boundaries decreased to 11.1% from 15% at 1310°C.

If a small recrystallized grain structure is obtained at 600°C, the liquid filler metals diffuse and penetrate into many grain boundaries.
It seems that the initial large grains remained and the recrystallization occurred in the initial large grains.
The increase in equivalent strain leads to increase in dislocation density, the number of nucleation sites, and the forces driving recrystallization.
It seems that the deceased number of precipitates less than 0.8 µm in diameter leads to an increased number of nuclei near nucleation sites (deformation bands, transition bands, particles, etc.) for recrystallization.
It reveals the grain structure using 5° and 15° misorientation angles of the grain boundary.

Grain Distribution.
Through the investigation and dimension measurement to different size of micro grinding tool, the distribution of CBN grains on the surface of the substrate could be accomplished and it could be described by G0 which stands for number of grains within 1mm2 of square on surface of the substrate.
Number of abrasive particle on the surface of micro grinding tools Particle size Grit size（μm） G0(Particle number in 1mm2) F800 22~25 700~1000 F1200 4~6 7000~8000 F3000 2~3 12000~14000 Surface Topography Analysis.
From the result it is concluded that large number of grains could turn to low Ra, the F3000# particle size reach a roughness of 0.086μm.
A novel micro shaft grinding tool is fabricated by cold sprayed with CBN grains, G0 which stands for number of grains within 1mm2 of square on surface of the substrate is discussed in this study, it is found that the value of G0 only depends on the particle size which is verified in the investigation and the G0 to different particle size is showed in Table.2.The manufacturing is carried out on a micro desktop machine developed by NEU.

In this paper, it’s reported that microwave calcination method could succeed in obtaining homogeneous grain growth and fine grain with a narrow grain size distribution.
Magnetic Properties Of Microwave Calcined Powders Number (emu/g) (emu/g) (Oe) F1140-20 62.804 32.694 3904 F1140-30 68.37 35.307 3798.5 F1140-40 68.63 35.472 3354.6 In table1, we list the magnetic properties of the powders calcined in microwave furnace at 1140℃ for 20min, 30min and 40min, respectively.
With the increased calcinations time, the grain shape became more platelet shaped and the grain size increased.
Magnetic Properties Of Microwave Calcined Balls Number (emu/g) (emu/g) (Oe) Q1140-20 66.586 33.989 3109.5 Q1140-30 69.022 36.075 3747.5 Q1140-40 70.322 36.182 3343.1 A sample which manufactured by classical ceramic process was supplied for comparing.
Microwave calcination method can succeed in obtaining homogeneous grain growth and fine grains.